import java.util.Scanner;

public class 无参无返 {
    public static void triangle(){
        Scanner sc=new Scanner(System.in);
        System.out.println("请输入底");
        int a = sc.nextInt();
        System.out.println("请输入高");
        int b = sc.nextInt();
        double area=a*b*0.5;
        System.out.println("该三角形面积为"+area);
    }
    public static void square(){
        Scanner sc=new Scanner(System.in);
        System.out.println("请输入长");
        int a = sc.nextInt();
        System.out.println("请输入宽");
        int b = sc.nextInt();
        double area=a*b;
        System.out.println("该正方形面积为"+area);
    }
    public static void rectangle(){
        Scanner sc=new Scanner(System.in);
        System.out.println("请输入长");
        int a = sc.nextInt();
        System.out.println("请输入宽");
        int b = sc.nextInt();
        double area=a*b;
        System.out.println("该长方形面积为"+area);
    }



    public static void main(String[] args) {
        triangle();
    }
}
